A supermassive black hole at the center of the Milky Way could swallow a gas cloud heading towards it which could generate flares of radiation, astronomers say.

The astronomers, who spotted the suicidal cloud from the Very Large Telescope array in Chile, said they were surprised to see the unusually dense cloud, not much bigger than our solar system and carrying about three times the mass of Earth.

"We have been looking at the galactic centre for 20 years, but mainly to observe the motion of stars," says Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany.

The team said the cloud, which path was revealed in earlier images, is moving at almost 2500 kilometres per second towards the Milky Way's black hole, Sagittarius A*.

Astronomers said that Sagittarius A* is at present strangely quiet and gets much less gas, and for some reason this starvation state makes the black hole much less efficient than a quasar, producing only a thousandth as much radiation per kilogram of fuel.

Normally a star would just sail past our black hole unscathed, but the loose mass of gas heading towards it is more vulnerable, astronomers said, adding that when it gets closer in 2013 the black hole's gravity will cause it to crash into the halo of hot gas around hole.

When the gaseous collision happens, this will send shockwaves through the cloud to ehat it to several million degrees which will shred the clouds into filaments, the astronomers said. And based on their simulations, the cloud could end up swirling right down into the black hole.

"By dumping more material in there, the cloud could drive the system into a higher efficiency regime," Genzel said.

The result may be one huge flare of radiation or several over the coming decades, but according to the astronomers, there's no danger of the active black hole harming Earth.